Adjustable potentiometer



Dec. l, E964 R. F. KLUG @ML350 ADJUSTABLE POTENTIOMETER Filed April 15, 196s United States Patent 3,161,350 ADSUS'EABLE PTENTMETER Robert F. Klug, Columbus, Nebr., assigner to Dale Electronics, inc., Columbus, Nebr. Filed Apr. 15, 1963, Ser. No. 272,957 4 crains. (ci. 33am-ras) This invention relates generally to potentiometer structures and more particularly to adjustable potentiometers suitable for voltage division in electronic, electric, and electo-mechanical systems.

It is an object of this invention to provide a rotary potentiometer wherein the value of the resistance may be readily adjusted.

It is another object of this invention to provide a rotary potentiometer manufactured with a preset resistance value, and wherein the value may be readily varied to obtain either a linear or a non-linear function upon a full sweep of the adjustment wiper arm.

Yet another object of this invention is to provide a rotary potentiometer manufactured with a preset resistance value as determined by a printed circuit of resistance elements arranged in parallel, with a wiper arm movable in engagement with one of the elements, and wherein the resistance value of the circuit can be readily varied from time to time by merely opening, for example, certain sections of the circuit.

Still another object of this invention is to provide a rotary potentiometer utilizing a printed circuit of resistance elements arranged in parallel, and being of a non-linear category, and wherein the value may selectively be frequently changed by merely opening, and closing if necessary, certain sections of the circuit without removing any internal parts of the potentiometer.

Yet another object of this invention is to provide an adjustable potentiometer which is rugged, simple in construction, reliable, and easily and accurately assembled.

These objects, and other features and advantages of this invention, will become readily apparent upon reference to the following description when taken with the accompanying drawings, wherein:

FIG. 1 is a partially exploded View of certain internal elements of the potentiometer of this invention;

FIG. 2 is a cross-sectional view of the potentiometer of this invention;

FG. 3 is a top plan View of the plate and the printed circuit thereon of FIG. 1;

FIG. 4 is a graph showing the resistance out/travel curve of the circuit of FlG. 3;

FlGS.v 5 and 6 are views, respectively, of an altered circuit and the graph therefor, the latter showing a nonlinear functon of the particular alteration of the circuit; and

FIGS. 7 and S are views similar to FIGS. 5 and 6 of another altered circuit and the graph therefor.

Referring now to the drawings, the adjustable potentiometer of this invention is indicated generally at l@ in FIG. 2. It comprises a case lll of non-conducting material the lower half l2 of which is annular with a relatively fiat bottom wall 13,an annular side wall ld and having a circular chamber 16 formed within the side wall 14. Y

The upperhalf 17 of the case 11 is annular and has a thickness substantially that of the bottom Wall 13. It has a shoulder 1S which is adapted for a complementary fit with a shoulder 19 formed on the upper periphery of the lower half l2, and forming thereby a groove 2l. To seal the two halves together, obviating thereby the entry of dust and other foreign particles into the chamber le, a releasable retaining ring 2 is provided, the lower ilange 23 of which extends into the groove Z1.

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Within the chamber lo, and on the floor 24 of the bottom Wall 13, a non-conductive flat plate 26, shown here as being circular, is secured. The plate 26 has an opening 27 formed at its center and has an electric circuit, indicated generally at 2S (FIG. l) disposed thereon Such as may be conveniently formed by conventional printed circuit techniques. Circuits of the type herein contemplated can be created on plate 26 in a plurality of ways, such as by deposition, etching or molding. For con venience, all such circuits will hereinafter be referred to as printed circuits. The circuit 28 includes an outer linear, arcuate first resistance element 29 (FIGS) arranged concentrically to the opening 27 and the ends of which are electrically connected to a pair of terminals 3l and 32 extended through the case 11 for external electrical connection. The circuit 28 includes additionally four more arcuate resistance elements 33, 34, 35 and 36 each spaced radially from the others and from the element 29, and all arranged concentrically about the opening Z7. The values of the resistance elements can be preset each at any predetermined amount.

A plurality of linear, radially extended connections 37a, 37b, 37C, 37d, 37e 371, 37g, 37h, 371', 37j, 37k, and 371 (FIG. 3) interconnect the resistances as illustrated, each connection arcuately equally spaced from the two adjacent connections, and being of the same length and material. The arrangement is such that a substantially infinite plurality of combinations of sections of resistances arranged in parallel is provided, the purpose of which will be described hereinafter.

Referring to FIGS. 1 and 2, a shaft 5d is inserted through a bearing 39 mounted in the lower half 12, and which shaft has a portion extended through the plate opening 27 centrally of the chamber 16. The upper reduced end 42 of the shaft 38 is journaled within another bearing 43 mounted in the upper half 17 of the case f1, and with a portion ld of the shaft extended eX- ternally of the case lll for rotation. A snap ring d6 or the like is secured to the shaft 38 and rotatable Within a groove 47 provided in the lower half 12, to prevent longitudinal movement of the shaft 3S.

Above the plate 26 and the printed circuit thereon is mounted a circular wiper arm 48 (FIGS. 1 and 2) of conductive material having a wiper element 49 formed on the periphery thereof and having a central opening 45' through which the shaft 38 extends. The wiper element 49 is engaged with the first resistance element ZL and is held thereagainst by a circular holder 5d of conductive material. The wiper arm 48 is provided with a plurality of arcuately spaced tabs 51 adapted to be bent into locking engagement each with one of a plurality of notches 55 formed in arcuately spaced relation in the periphery of the holder 5t).

The holder 5ft has a central opening (not shown) for alignment with the wiper arm opening d5', and through which the shaft 33 extends. To mount the wiper arm 48 and the holder 5@ as a unit, a sleeve dit is provided which is secured to the shaft 38 by any conventional means such as a lock nut o5, and which insulates the shaft from the arm d8 and holder 59.

Embracing the sleeve 6ft for rotation therewith in response to rotation of the shaft 38 is an annular return member 52 of conductive material. The return member 52 is engaged with the holder 5u so as to conduct electricity therefrom, and has a groove 53 formed in the upper end thereof. To transmit the return current from the return member 52, a collector unit 54 (FIGS. 1 and 2) is provided.

The unit 5d includes a bolt terminal 56 both ends 57 and 53 of which are threaded, with a nut 59 threaded on the exterior end 57, and with a linger device 61 held on the interior end 58 by another nut 62. The finger device 6l is U-shaped wherein the base 63 has an opening (not shown) through which the bolt S6 passes, and wherein a pair of flexible, parallel fingers 64 and 66 are adapted to and do frictionally engage the return member 52 within its grooves S3.

Referring now to FIG. 4, assuming the vertical slant R as viewed, of the graph to represent resistance out, and the horizontal slant WAT to represent the travel of the wiper arrn 48 from the zero resistance end of the element 29 to the other end thereof, the resistance value function line L shows a linear effect.

Referring to FlGS. and 6, selected connections and resistances of the modified circuit 28 have been opened. Starting from the junction of the innermost resistance 36 and the connection 371, which junction has been opened, a convolute curve of openings has been made. urning now to FIG. 6, it is seen that the resistance at line L' is non-linear, the function being Varied.

In FIG. 7, the original circuit 23 has again been modified to one 28 wherein it will be noted that each connection 37e-37! has been opened between the first element 29 and the next element 33. Referring to the graph in FiG. 8, it is seen that upon removing or cutting out all the sections of the circuit 2S" except the element 29, the resistance out/travel function L is again a linear effect. It should be noted that the more sections of the circuit 2S which are removed, the more the resistance value of the circuit.

In summation, an adjustable potentiometer has been described herein which is of a rotary type having a plurality of resistance elements arranged in parallel in a printed-type circuit, wherein the circuit may be altered at the will of the user to vary the value of the resistance.

Some changes may be made in the construction and arrangement of my adjustable potentiometer without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims, any modified forms of structure 0r use of mechanical equivalents which may be reasonably included within their scope.

I claim:

l. An adjustable potentiometer comprising in combination,

a case having a chamber formed therein,

a non-conductive plate secured within said chamber,

a printed circuit on said plate, said printed circuit including at least three arcuate resistance elements deposited on said plate, said resistance elements form,- i-ng segments of circles concentric about a center axis through said plate, said arcuate resistance elements being electrically connected in parallel by radial conductive elements, and a plurality of additional radial conductive elements spaced circumferentially around said axis and interconnecting said resistance elements,

said arcuate resistance elements and conductive elements being adapted to be selectively opened at at least one predetermined point whereby the resistance value of said circuit is varied,

a pair of leads connected to said conductive elements,

a rotatable shaft positioned within said case so as t0 project within said chamber and to project therefrom,

a conductive contact arm secured to said shaft and rotatable therewith, said contact arm insulated from said shaft and including a contact member engaging one of said arcuate resistance elements,

a conductive collector mounted on said shaft, insulated therefrom, and engaged with said Contact arm, and

conductive means secured to said case, extended within said chamber, engaged with said collector, and adapted for electrical connection externally of said case.

2. The potentiometer of claim l wherein said three resistance elements terminate at common radial lines.

3. An adjustable potentiometer comprising in cornbination,

a case having a chamber formed therein,

a non-conductive plate secured within said chamber,

a printed circuit `on said plate, said printed circuit including a plurality of spaced apart arcuate resistance elements deposited on said plate, said resistance elements forming segments of circles concentric about a center axis through said plate, said arcuate resistance elements being electrically connected in parallel by radial conductive elements, and a plurality of additional radial conductive elements spaced circumferentially around said axis and interconnecting said resistance elements,

said arcuate resistance elements and conductive elements being adapted to be selectively opened at at least one predetermined point whereby the resistance value of said circuit is varied,

apair of leads connected to said conductive elements,

a rotatable shaft positioned within said case so as to project within said chamber and to project therefrom,

a conductive Contact arm secured to said shaft and rotatable therewith, said contact arm insulated from said shaft and including a contact member engaging one of said arcuate resistance elements,

a conductive collector mounted on said shaft, insulated therefrom, and engaged with said contact arm, and

conductive means secured to said case, extended within said chamber, engaged with said collector, and adapted for electrical connection externally of said case.

4. The method of making an adjustable potentiometer,

comprising,

making a case having a chamber formed therein,

depositing a printed circuit on a non-conductive plate with the circuit having three arcuate resistance elements forming segments of circles concentric about a center axis through the plate and connected in parallel by radial conductive elements and a plurality of additional radial conductive elements spaced circumferentially around the axis and interconnecting the arcuate resistance elements,

opening at least one of said elements including said arcuate resistance elements and said conductive elements at at least one predetermined point,

mounting the plate on a rotatable shaft within the chamber with the shaft projecting from the chamber,

securing a conductive contact arm to said shaft for rotation therewith and engagement with one of said arcuate resistance elements,

mounting a conductive collector on the shaft insulated therefrom and electrically engaging the contact arm, and

securing conductive means to the case and extending the same into the chamber into engagement with the collector.

References Cited by the Examiner UNITED STATES PATENTS RICHARD M. WOOD, Primary Examiner. 

1. AN ADJUSTABLE POTENTIOMETER COMPRISING IN COMBINATION, A CASE HAVING A CHAMBER FORMED THEREIN, A NON-CONDUCTIVE PLATE SECURED WITHIN SAID CHAMBER, A PRINTED CIRCUIT ON SAID PLATE, SAID PRINTED CIRCUIT INCLUDING AT LEAST THREE ARCUATE RESISTANCE ELEMENTS DEPOSITED ON SAID PLATE, SAID RESISTANCE ELEMENTS FORMING SEGMENTS OF CIRCLES CONCENTRIC ABOUT A CENTER AXIS THROUGH SAID PLATE, SAID ARCUATE RESISTANCE ELEMENTS BEING ELECTRICALLY CONNECTED IN PARALLEL BY RADIAL CONDUCTIVE ELEMENTS, AND A PLURALITY OF ADDITIONAL RADIAL CONDUCTIVE ELEMENTS SPACED CIRCUMFERENTIALLY AROUND SAID AXIS AND INTERCONNECTING SAID RESISTANCE ELEMENTS, SAID ARCUATE RESISTANCE ELEMENTS AND CONDUCTIVE ELEMENTS BEING ADAPTED TO BE SELECTIVELY OPENED AT AT LEAST ONE PREDETERMINED POINT WHEREBY THE RESISTANCE VALUE OF SAID CIRCUIT IS VARIED, A PAIR OF LEADS CONNECTED TO SAID CONDUCTIVE ELEMENTS, A ROTATABLE SHAFT POSITIONED WITHIN SAID CASE SO AS TO PROJECT WITHIN SAID CHAMBER AND TO PROJECT THEREFROM, A CONDUCTIVE CONTACT ARM SECURED TO SAID SHAFT AND ROTATABLE THEREWITH, SAID CONTACT ARM INSULATED FROM SAID SHAFT AND INCLUDING A CONTACT MEMBER ENGAGING ONE OF SAID ARCUATE RESISTANCE ELEMENTS, A CONDUCTIVE COLLECTOR MOUNTED ON SAID SHAFT, INSULATED THEREFROM, AND ENGAGED WITH SAID CONTACT ARM, AND CONDUCTIVE MEANS SECURED TO SAID CASE, EXTENDED WITHIN SAID CHAMBER, ENGAGED WITH SAID COLLECTOR, AND ADAPTED FOR ELECTRICAL CONNECTION EXTERNALLY OF SAID CASE. 